Property matter of my parents

My parents made a will somewhere in the year 2003 that their bungalow should be given to her five sons after their death. The will was done by my parents, my one brother (who must have influenced my parents) and my one sister. We are in all 5 brothers and 4 sisters. None of the 4 brothers and 3 sisters were aware about the will, except my one brother and my one sister. My father passed away in 2008 and my mother is stilling living. Now my this one brother (who is in New Zealand for past 12 years) is suggesting that he will make an Affidavit stating that the bungalow will be transferred to all 5 brothers and he needs signatures of all 4 sisters. I do not want to give my signature because the will was basically done by my brother who influenced my parents. All my other 3 sisters will sign the Affidavit. He said after my mother's death, the Will be opened in the High Court and then you can fight in the court. He said my parents are giving you something little as mentioned in the will. Please advice what is the right solution for this, as I do not want to sign the Affidavit.